The prior patented art and commercial art contains teachings relating to insulating enclosures for valves and pipe fittings used in steam service and certain process industries. The prior art devices vary considerably in their natures, ranging from rigid modular enclosures through semi-rigid and flexible insulating enclosures.
For example, prior U.S. Pat. No. 4,207,918, issued Jan. 17, 1980, discloses a flexible insulation jacket for valves formed in several cooperating sections which are secured in assembled relationship on a valve by straps and buckles plus additional forms of releasable fasteners. The patented structure is rather complex and comparatively costly. Due to its modular form, it tends not to be universal in terms of compatibility with valves of different manufacturers.
U.S. Pat. No. 4,112,967, issued Sept. 12, 1978 shows a further example of the prior art. This patented structure possesses generally the same drawbacks noted above in connection with U.S. Pat. No. 4,207,918. Neither prior patent discloses a unitary universal insulating jacket for valves and pipe fittings which is entirely flexible and initially flat before being applied to a valve or fitting, and which utilizes convenient drawstrings for tightly but removably attaching the jacket to a valve or fitting in an almost airtight engagement with opposing rigid surfaces and contours of the valve or fitting.
Another known prior art structure for the thermal insulation of valves is manufactured and sold by Hitco Insulation Products, subsidiary of Armco, 1600 W. 135th St., Gardena, Calif. 90249. The Hitco product is a semi-flexible insulation jacket or blanket which is manually compressed and shaped to roughly conform to the external contours of a valve, and then tied in place by lacing wires which are engaged with headed pins fixed to the exterior of the device. The prior art structure is more costly than the flexible insulation jacket according to the present invention and is much less convenient to use, and does not have the ability of the invention to be drawn into tight sealing relationship with a valve or fitting while conforming snugly with its external contours, by virtue of draw cords. The present invention is therefore thought to be a very significant advance over all of the above prior art devices for a broadly similar purpose.